The present invention is directed to a method and apparatus for providing improved isolation for testing a subpart of a system. More specifically, the present invention is directed to a method and apparatus by which a modular component of a system can be at least partly isolated from stresses that are applied to the rest of the system as a part of a test.
An important part of any attempt to deploy a newly designed system is the process of ascertaining whether the finally designed product will in fact operate at the required efficiencies and for a desired duration of time in the various physical environments in which it will be placed.
One technique by which devices are tested is to subject them to extreme temperature and vibration testing in a test chamber. The intent of the tests is to approximate what the expected life span of the device will be in its intended environment as well as to approximate the extreme environmental limits. Two commonly applied tests are the Highly Accelerated Life Test (HALT) and the Highly Accelerated Stress Screen (HASS). The HALT over stresses the device far beyond the intended end use environment looking for weaknesses and is commonly used during the design phase of a device. The HASS is similar to the HALT but is often used during the manufacturing phase as a screening test prior to installing the devices in the field.
One example of a system that would require such analysis is communications equipment, including wireless communications equipment, to be installed in the field. This type of equipment may include one or more circuit boards whose operation may be adversely affected by temperature and other environmental variables. In communications equipment, it is not uncommon for the system in question to include a plurality of modules or boards, some of which are more susceptible to damage in these tests than others. For example, one such xe2x80x9cweakerxe2x80x9d module might be a power supply board of a multi-circuit board system. The power supply might be a AC/DC converter that is known to be subject to failure if operated at a temperature outside he range of xe2x88x9210xc2x0 to +80xc2x0 C. or at a vibration of greater than 10 Grms (Gravity root mean square). However, the test conditions for the system using the power supply may be in the range of xe2x88x9270xc2x0 to +90xc2x0 C. and up to 29 Grms. For example, this can be desirable when testing more robust system components other than the module. Therefore, if the power supply is placed in the chamber with the rest of the system during such a test, it will likely fail and have a negative impact on the test of the rest of the system.
One solution to this problem is to place the weaker module outside the chamber in which the HALT or HASS tests are being applied. This has a drawback, however, as the electrical distance of separation between the module (outside the chamber) and the rest of the system (inside the chamber) may itself prevent the overall system from operating correctly. For example, in some systems, the electrical distance between components is important to timing (e.g., synchronization) between components. Also, this arrangement generally leads to unwieldy and complicated electrical interfaces between the module and the rest of the system, e.g., a separate wire must be run from each active pin on the module through the walls of the test chamber to the appropriate place in the rest of the system. It is therefore desirable to have a test chamber with the remainder of the system that is being subjected to testing.
The present invention provides a method and apparatus for substantially isolating a module from the rest of the system of which the module is a part. In particular, the present invention provides an isolation container (xe2x80x9cboxxe2x80x9d) it which a weaker module is disposed. One embodiment of the present invention comprises a box including damping elements so as to reduce the effect of vibration on the isolated module. In another embodiment, the box is equipped to receive compressed air that flows over the weaker module so as to maintain the module at an appropriate temperature. The box is designed to allow the module (e.g., a daughter board that plugs into a mother board) to be electrically connected to the rest of the system (e.g., the mother board with other modules) that is being subjected to the stress test. As used herein, the term xe2x80x9cconnectxe2x80x9d is meant to encompass both direct and indirect connection. Thus A can be connected to B directly. Also A is xe2x80x9cconnectedxe2x80x9d to B if A is directly connected to C, and C is directly connected to B. A is xe2x80x9cdirectlyxe2x80x9d connected to B if it sends signals through any medium from A to B. Thus, A can be directly connected to B via a wire, a soldered connection, an infrared link, an electromagnetic (e.g RF) link, etc.
One skilled in the art will understand that besides circuit boards for use in wireless communications, the invention can be used in other environments and should be understood to cover these other embodiments beyond those specifically described herein. For instance, certain system components include modules of varying strengths such that when the system is exposed to particular stress testing, one or more of the modules is at risk of failure or damage due to the stress testing.